Limited-slip driveline apparatus

Abstract

The present disclosure relates to a limited-slip clutch system and method. In one aspect, the limited-slip clutch actuation system can include a hydraulic pump operated by a variable speed drive wherein the pump can be configured to generate hydraulic flow in a hydraulic circuit including an actuation branch line that actuates a clutch. The circuit may also include a flow regulating valve for regulating a hydraulic fluid flow rate through the hydraulic circuit wherein the flow regulating valve can be configured to prevent the hydraulic fluid flow rate from exceeding a set maximum flow rate regardless of a magnitude of the hydraulic pressure in the hydraulic circuit. In operation, the pump speed can be controlled based on a command pressure set point and the measured pressure in the actuation branch line and to minimize operational costs by operating the pump at a transition region of the system pressure-pump speed curve.

What is claimed is: 
     
       1. A method for controlling the actuation of a clutch in a limited-slip driveline apparatus, the method including the steps of:
 a. providing a hydraulic pump operated by a variable speed drive, the pump being configured to generate hydraulic flow in a hydraulic circuit including an actuation branch line that actuates the clutch; and 
 b. providing a flow regulating valve for regulating a hydraulic fluid flow rate through the hydraulic circuit, the flow regulating valve including a variable-size outlet orifice being configured to prevent the hydraulic fluid flow rate from exceeding a predetermined maximum flow rate regardless of a magnitude of the hydraulic pressure in the hydraulic circuit upstream of the flow regulating valve; 
 c. providing an electronic control system including a controller configured to receive an input signal from a pressure sensor located in the actuation branch line and configured to send an output pump speed signal to the pump variable speed drive; 
 d. the hydraulic circuit having:
 i. a first operating region; 
 ii. a second operating region within which, in comparison to the first operating region, the pump speed is higher and the pressure in the actuation branch line is both greater and less linear with the speed of the pump; and 
 iii. a transition region between the first and second operating regions; 
 
 e. receiving a commanded pressure value and the pressure sensor input signal at the controller; 
 f. calculating the output pump speed signal based on the commanded pressure value and the input signal from the pressure sensor, wherein the output pump speed signal is set to a speed that will place the hydraulic circuit within the transition region when the commanded pressure value would place the hydraulic circuit in the second operating region; and 
 g. sending the output pump speed signal to the variable speed drive. 
 
     
     
       2. The method for controlling the actuation of a clutch of  claim 1 , wherein the transition region includes pump speeds in the range from 1050 rpm to 1150 rpm. 
     
     
       3. The method for controlling the actuation of a clutch of  claim 1 , wherein the step of calculating the pump output speed signal includes subtracting the pressure sensor input signal from the commanded pressure value to create a pressure error value. 
     
     
       4. The method for controlling the actuation of a clutch of  claim 1 , wherein the variable-sized outlet orifice of the flow regulating valve is formed by a plurality of first openings in a valve sleeve and a plurality of second openings in a valve piston that is spring-biased toward an open position within the valve sleeve. 
     
     
       5. A limited-slip clutch actuation system comprising:
 a. a hydraulic pump operated by a variable speed drive, the pump being configured to generate hydraulic flow in a hydraulic circuit including an actuation branch line that actuates a clutch; and 
 b. a flow regulating valve for regulating a hydraulic fluid flow rate through the hydraulic circuit, the flow regulating valve including a variable-size outlet orifice being configured to prevent the hydraulic fluid flow rate from exceeding a predetermined maximum flow rate regardless of a magnitude of the hydraulic pressure in the hydraulic circuit upstream of the flow regulating valve; 
 c. the hydraulic circuit having:
 i. a first operating region; 
 ii. a second operating region within which, in comparison to the first operating region, the pump speed is higher and the pressure in the actuation branch line is both greater and less linear with the speed of the pump; and 
 iii. a transition region between the first and second operating regions; 
 
 d. an electronic control system including a controller configured to receive an input signal from a pressure sensor located in the actuation branch line and configured to send an output pump speed signal to the pump variable speed drive, the electronic control system being configured to calculate the output pump speed signal based on a commanded pressure value and the input signal from the pressure sensor, and configured to set the output pump speed signal to a speed that will place the hydraulic circuit within the transition region when the commanded pressure value corresponds to a pressure that would place the hydraulic circuit in the non-linear operating region. 
 
     
     
       6. The limited-slip clutch actuation system of  claim 5 , wherein the transition region includes pump speeds in the range from 1050 rpm to 1150 rpm. 
     
     
       7. The limited-slip clutch actuation system of  claim 5 , wherein the commanded pressure value is set to 400 psi.